DTLS Encapsulation of SCTP Packets
draft-ietf-tsvwg-sctp-dtls-encaps-04
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 8261.
|
|
|---|---|---|---|
| Authors | Michael Tüxen , Randall R. Stewart , Randell Jesup , Salvatore Loreto | ||
| Last updated | 2014-05-13 | ||
| Replaces | draft-tuexen-tsvwg-sctp-dtls-encaps | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Formats | |||
| Reviews | |||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | WG Document | |
| Document shepherd | (None) | ||
| IESG | IESG state | Became RFC 8261 (Proposed Standard) | |
| Consensus boilerplate | Unknown | ||
| Telechat date | (None) | ||
| Responsible AD | Spencer Dawkins | ||
| Send notices to | (None) |
draft-ietf-tsvwg-sctp-dtls-encaps-04
Network Working Group M. Tuexen
Internet-Draft Muenster Univ. of Appl. Sciences
Intended status: Standards Track R. Stewart
Expires: November 14, 2014 Adara Networks
R. Jesup
WorldGate Communications
S. Loreto
Ericsson
May 13, 2014
DTLS Encapsulation of SCTP Packets
draft-ietf-tsvwg-sctp-dtls-encaps-04.txt
Abstract
The Stream Control Transmission Protocol (SCTP) is a transport
protocol originally defined to run on top of the network protocols
IPv4 or IPv6. This document specifies how SCTP can be used on top of
the Datagram Transport Layer Security (DTLS) protocol. Using
encapsulation method described in this document, SCTP is agnostic
about the protocols being used below DTLS, explicit IP addresses can
not be used in the SCTP control chunks. As a consequence, the SCTP
associations are single homed.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on November 14, 2014.
Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
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include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. Encapsulation and Decapsulation Procedure . . . . . . . . . . 3
4. General Considerations . . . . . . . . . . . . . . . . . . . 3
5. DTLS Considerations . . . . . . . . . . . . . . . . . . . . . 3
6. SCTP Considerations . . . . . . . . . . . . . . . . . . . . . 4
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
8. Security Considerations . . . . . . . . . . . . . . . . . . . 5
9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 5
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Overview
The Stream Control Transmission Protocol (SCTP) as defined in
[RFC4960] is a transport protocol running on top of the network
protocols IPv4 [RFC0791] or IPv6 [RFC2460]. This document specifies
how SCTP is used on top of the Datagram Transport Layer Security
(DTLS) protocol defined in [RFC6347]. This encapsulation is used for
example within the WebRTC protocol suite (see
[I-D.ietf-rtcweb-overview] for an overview) for transporting
non-(S)RTP data between browsers. The architecture of this stack is
described in [I-D.ietf-rtcweb-data-channel].
Please note that the procedures defined in [RFC6951] for dealing with
the UDP port numbers do not apply here. When using the encapsulation
defined in this document, SCTP is agnostic about the protocols used
below DTLS.
2. Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
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3. Encapsulation and Decapsulation Procedure
When an SCTP packet is provided to the DTLS layer, the complete SCTP
packet, consisting of the SCTP common header and a number of SCTP
chunks, MUST be handled as the payload of the application layer
protocol of DTLS. When the DTLS layer has processed a DTLS record
containing a message of the application layer protocol, the payload
MUST be given up to the SCTP layer. The SCTP layer expects an SCTP
common header followed by a number of SCTP chunks.
4. General Considerations
An implementation of SCTP over DTLS MUST implement and use a path
maximum transmission unit (MTU) discovery method that functions
without ICMP to provide SCTP/DTLS with an MTU estimate. An
implementation of "Packetization Layer Path MTU Discovery" [RFC4821]
either in SCTP or DTLS is RECOMMENDED.
5. DTLS Considerations
The DTLS implementation MUST be based on DTLS 1.2 [RFC6347]. The
support of future versions of DTLS is RECOMMENDED if defined.
If path MTU discovery is performed by the DTLS layer, the method
described in [RFC4821] MUST be used. For probe packets, the
extension defined in [RFC6520] MUST be used.
If path MTU discovery is performed by the SCTP layer and IPv4 is used
as the network layer protocol, the DTLS implementation MUST allow the
DTLS user to enforce that the corresponding IPv4 packet is sent with
the Don't Fragment (DF) bit set. If controlling the DF bit is not
possible, for example due to implementation restrictions, a safe
value for the path MTU has to be used by the SCTP stack.
The DTLS implementation SHOULD allow the DTLS user to set the
Differentiated services code point (DSCP) used for IP packets being
sent. This requires the DTLS implementation to pass the value
through and the lower layer to allow setting this value. If the
lower layer does not support setting the DSCP, then the DTLS user
will end up with the default value used by protocol stack. Please
note that only a single DSCP value can be used for all packets
belonging to the same SCTP association.
Using explicit congestion notifications (ECN) in SCTP requires the
DTLS layer to pass the ECN bits through and its lower layer to expose
access to them for sent and received packets. If this is not
possible, for example due to implementation restrictions, ECN can't
be used by SCTP.
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SCTP performs segmentation and reassembly based on the path MTU.
Therefore the DTLS layer MUST NOT use any compression algorithm.
The DTLS MUST support sending messages larger than the current path
MTU. This might result in sending IP level fragmented messages.
6. SCTP Considerations
This section describes the usage of the base protocol and the
applicability of various SCTP extensions.
6.1. Base Protocol
This document uses SCTP [RFC4960] with the following restrictions,
which are required to reflect that the lower layer is DTLS instead of
IPv4 and IPv6 and that SCTP doesn't deal with the IP addresses or the
transport protocol used below DTLS:
o A DTLS connection MUST be established before an SCTP association
can be set up.
o All SCTP associations are single-homed. Therefore it is
RECOMMENDED to set the SCTP parameter path.max.retrans to
association.max.retrans.
o The INIT and INIT-ACK chunk MUST NOT contain any IPv4 Address or
IPv6 Address parameters. The INIT chunk MUST NOT contain the
Supported Address Types parameter.
o The implementation MUST NOT rely on processing ICMP or ICMPv6
packets. This applies in particular to path MTU discovery when
performed by SCTP.
6.2. Padding Extension
The padding extension defined in [RFC4820] MUST be supported and used
for probe packets when performing path MTU discovery as specified in
[RFC4821].
6.3. Dynamic Address Reconfiguration Extension
If the dynamic address reconfiguration extension defined in [RFC5061]
is used, only wildcard addresses MUST be used in ASCONF chunks.
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6.4. SCTP Authentication Extension
The SCTP authentication extension defined in [RFC4895] can be used
with DTLS encapsulation, but does not provide any additional benefit.
6.5. Partial Reliability Extension
Partial reliability as defined in [RFC3758] can be used in
combination with DTLS encapsulation. It is also possible to use
additional PR-SCTP policies.
6.6. Stream Reset Extension
The SCTP stream reset extension defined in [RFC6525] can be used with
DTLS encapsulation. It is used to reset SCTP streams and add SCTP
streams during the lifetime of the SCTP association.
6.7. Interleaving of Large User Messages
SCTP as defined in [RFC4960] does not support the interleaving of
large user messages that need to be fragmented and reassembled by the
SCTP layer. The protocol extension defined in
[I-D.ietf-tsvwg-sctp-ndata] overcomes this limitation and can be used
with DTLS encapsulation.
7. IANA Considerations
This document requires no actions from IANA.
8. Security Considerations
Security considerations for DTLS are specified in [RFC6347] and for
SCTP in [RFC4960], [RFC3758], and [RFC6525]. The combination of SCTP
and DTLS introduces no new security considerations.
It should be noted that the inability to process ICMP or ICMPv6
messages does not add any security issue. The processing of these
messages for SCTP carried over a connection-less lower layer like IP,
IPv6 or UDP is required to protect nodes not supporting SCTP. Since
DTLS provides a connection-oriented lower layer, this kind of
protection is not necessary.
9. Acknowledgments
The authors wish to thank Gorry Fairhurst, Joe Touch and Magnus
Westerlund for their invaluable comments.
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10. References
10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4820] Tuexen, M., Stewart, R., and P. Lei, "Padding Chunk and
Parameter for the Stream Control Transmission Protocol
(SCTP)", RFC 4820, March 2007.
[RFC4821] Mathis, M. and J. Heffner, "Packetization Layer Path MTU
Discovery", RFC 4821, March 2007.
[RFC4960] Stewart, R., "Stream Control Transmission Protocol", RFC
4960, September 2007.
[RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security Version 1.2", RFC 6347, January 2012.
[RFC6520] Seggelmann, R., Tuexen, M., and M. Williams, "Transport
Layer Security (TLS) and Datagram Transport Layer Security
(DTLS) Heartbeat Extension", RFC 6520, February 2012.
10.2. Informative References
[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, September
1981.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, December 1998.
[RFC3758] Stewart, R., Ramalho, M., Xie, Q., Tuexen, M., and P.
Conrad, "Stream Control Transmission Protocol (SCTP)
Partial Reliability Extension", RFC 3758, May 2004.
[RFC4895] Tuexen, M., Stewart, R., Lei, P., and E. Rescorla,
"Authenticated Chunks for the Stream Control Transmission
Protocol (SCTP)", RFC 4895, August 2007.
[RFC5061] Stewart, R., Xie, Q., Tuexen, M., Maruyama, S., and M.
Kozuka, "Stream Control Transmission Protocol (SCTP)
Dynamic Address Reconfiguration", RFC 5061, September
2007.
[RFC6525] Stewart, R., Tuexen, M., and P. Lei, "Stream Control
Transmission Protocol (SCTP) Stream Reconfiguration", RFC
6525, February 2012.
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[RFC6951] Tuexen, M. and R. Stewart, "UDP Encapsulation of Stream
Control Transmission Protocol (SCTP) Packets for End-Host
to End-Host Communication", RFC 6951, May 2013.
[I-D.ietf-rtcweb-overview]
Alvestrand, H., "Overview: Real Time Protocols for Brower-
based Applications", draft-ietf-rtcweb-overview-09 (work
in progress), February 2014.
[I-D.ietf-rtcweb-data-channel]
Jesup, R., Loreto, S., and M. Tuexen, "WebRTC Data
Channels", draft-ietf-rtcweb-data-channel-08 (work in
progress), April 2014.
[I-D.ietf-tsvwg-sctp-ndata]
Stewart, R., Tuexen, M., Loreto, S., and R. Seggelmann, "A
New Data Chunk for Stream Control Transmission Protocol",
draft-ietf-tsvwg-sctp-ndata-00 (work in progress),
February 2014.
Authors' Addresses
Michael Tuexen
Muenster University of Applied Sciences
Stegerwaldstrasse 39
48565 Steinfurt
DE
Email: tuexen@fh-muenster.de
Randall R. Stewart
Adara Networks
Chapin, SC 29036
US
Email: randall@lakerest.net
Randell Jesup
WorldGate Communications
3800 Horizon Blvd, Suite #103
Trevose, PA 19053-4947
US
Phone: +1-215-354-5166
Email: randell_ietf@jesup.org
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Salvatore Loreto
Ericsson
Hirsalantie 11
Jorvas 02420
FI
Email: Salvatore.Loreto@ericsson.com
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